Summary The ultimate goal of our project is to develop novel therapeutics effective in chronic kidney diseases, such as diabetic nephropathy (DN), that normally develop fibrosis, lead to end stage renal disease and require renal replacement therapy. DN is a complication of diabetes and is characterized by thickening of the glomerular basement membrane and mesangial expansion, with progression into glomerulosclerosis, tubular necrosis, and interstitial fibrosis that ultimately results in renal failure. Around 177 million people have diabetes mellitus worldwide, and it has been estimated that this number will increase to 360 million by 2030. Of these people, about 20-30% are expected to develop DN. This SBIR phase 2B application builds on the results obtained in phase 2 where novel and selective small molecule antagonists of the lysophosphatidic acid receptor subtype 1 (LPA1R) were optimized for in vitro potency, ADME, drug-like properties and pharmacokinetics. EPGN696 emerged as an optimized lead compound which is effective in preserving proximal tubule structure and function, reducing both tubule interstitial fibrosis and macrophage infiltration in a mouse model of renal fibrosis (ureteral unilateral obstruction - UUO). LPA1R antagonism in this model led to marked reductions in pro-fibrotic and pro-inflammatory markers, including TNF- ?, TGF-?, CTGF, PDGF, ?-SMA, Col-IV. In a mouse model of type 1 diabetic kidney disease (F1Akita), EPGN696 provided organ protection by preventing and reversing mesangial matrix expansion. However, measures of urinary albumin excretion and albumin to creatinine ratio (ACR) values, which are important functional read outs in clinical practice, are not consistent in mouse models of DN. In addition, preliminary safety assessment in a non-GLP 14-day study in rats indicated EPGN696 was well tolerated up to 300 mg/kg dose. In this application, we propose to evaluate EPGN696 in rat models of type 1 (STZ) and type 2 (ZDF) diabetic kidney disease, which reflect the typical changes in urinary albumin excretion and ACR observed in humans. Moreover, the time course of robust ACR increases and plasma creatinine decreases in these rat models have been documented by our collaborative team. Prevention and reversal studies, either alone or in combination with a standard of care agent, Losartan are planned. EPGN696 will be evaluated in rat DN models, ZDF and STZ, following determination of systemic exposure to select a suitable therapeutic dose, in collaboration with Professors Kumar Sharma and Nigel Calcutt. Urinary metabolomic analysis will be performed to identify pathways that are elevated in the pathological state and can be modulated by EPGN696. Existing human metabolomic data will be compared with the rat data to establish common pathways and metabolites that could be useful clinically in stratifying patients for drug therapy. Additionally, IND-enabling studies will be conducted according to guidance received by the FDA. These studies will support opening an IND and initiation of phase 1 clinical trials in humans.